Invalid RGBA argument when use sq.pl.co_occurrence

When I used squidpy to draw Co-occurrence figure:

sq.gr.spatial_neighbors(adata)
sq.gr.nhood_enrichment(adata, cluster_key="Level1_Filt")
sq.pl.nhood_enrichment(adata, cluster_key="Level1_Filt",palette = 'tab20')
sq.gr.co_occurrence(adata, cluster_key="Level1_Filt")
sq.pl.co_occurrence(
adata,
cluster_key="Level1_Filt",
clusters="B",
figsize=(8, 4),
)

I got this error:

ValueError Traceback (most recent call last)
Cell In[115], line 1
----> 1 sq.pl.co_occurrence(
2 adata,
3 cluster_key="Level1_Filt",
4 clusters="B",
5 figsize=(8, 4),
6 )

File /squidpy/lib/python3.10/site-packages/squidpy/pl/_graph.py:365, in co_occurrence(adata, cluster_key, palette, clusters, figsize, dpi, save, legend_kwargs, **kwargs)
362 clusters = _assert_non_empty_sequence(clusters, name="clusters")
363 clusters = sorted(_get_valid_values(clusters, categories))
--> 365 palette = _get_palette(adata, cluster_key=cluster_key, categories=categories, palette=palette)
367 fig, axs = plt.subplots(
368 1,
369 len(clusters),
(...)
372 constrained_layout=True,
373 )
374 axs = np.ravel(axs) # make into iterable

File /squidpy/lib/python3.10/site-packages/squidpy/pl/_color_utils.py:50, in _get_palette(adata, cluster_key, categories, palette, alpha)
45 if len(palette) != len(categories):
46 raise ValueError(
47 f"Expected palette to be of length {len(categories)}, found {len(palette)}. "
48 + f"Removing the colors in adata.uns with adata.uns.pop('{cluster_key}_colors') may help."
49 )
---> 50 return {cat: to_hex(to_rgba(col)[:3] + (alpha,), keep_alpha=True) for cat, col in zip(categories, palette)}
51 except KeyError as e:
52 logg.error(f"Unable to fetch palette, reason: {e}. Using None.")

File /squidpy/lib/python3.10/site-packages/squidpy/pl/_color_utils.py:50, in (.0)
45 if len(palette) != len(categories):
46 raise ValueError(
47 f"Expected palette to be of length {len(categories)}, found {len(palette)}. "
48 + f"Removing the colors in adata.uns with adata.uns.pop('{cluster_key}_colors') may help."
49 )
---> 50 return {cat: to_hex(to_rgba(col)[:3] + (alpha,), keep_alpha=True) for cat, col in zip(categories, palette)}
51 except KeyError as e:
52 logg.error(f"Unable to fetch palette, reason: {e}. Using None.")

File/squidpy/lib/python3.10/site-packages/matplotlib/colors.py:299, in to_rgba(c, alpha)
297 rgba = None
298 if rgba is None: # Suppress exception chaining of cache lookup failure.
--> 299 rgba = _to_rgba_no_colorcycle(c, alpha)
300 try:
301 _colors_full_map.cache[c, alpha] = rgba

File /squidpy/lib/python3.10/site-packages/matplotlib/colors.py:374, in _to_rgba_no_colorcycle(c, alpha)
370 raise ValueError(
371 f"Invalid string grayscale value {orig_c!r}. "
372 f"Value must be within 0-1 range")
373 return c, c, c, alpha if alpha is not None else 1.
--> 374 raise ValueError(f"Invalid RGBA argument: {orig_c!r}")
375 # turn 2-D array into 1-D array
376 if isinstance(c, np.ndarray):

ValueError: Invalid RGBA argument: 'B'

How can I solve this problem?